Statistical vibrational autodetachment and radiative cooling rates of para-benzoquinone

Stockett, Mark H., Bull, James N. ORCID:, Schmidt, Henning T. and Zettergren, Henning (2022) Statistical vibrational autodetachment and radiative cooling rates of para-benzoquinone. Physical Chemistry Chemical Physics, 24 (19). pp. 12002-12010. ISSN 1463-9076

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We report measurements of the statistical vibrational autodetachment (VAD, also called thermionic emission) and radiative cooling rates of isolated para-benzoquinone (pBQ, C6H4O2) radical anions using the cryogenic electrostatic ion storage ring facility DESIREE. The results are interpreted using master equation simulations with rate coefficients calculated using statistical detailed balance theory. The VAD rate is determined by measuring the time-dependent yield of neutral pBQ due to spontaneous electron emission from a highly-excited ensemble of anions formed in an electron-attachment ion source. Competition with radiative cooling quenches the VAD rate after a critical time of τc = 11.00(5) ms. Master equation simulations which reproduce the VAD yield provide an estimate of the initial effective vibrational temperature of the ions of 1100(20) K, and provide insight into the anion formation scenario. A second measurement of the radiative cooling rate of pBQ− stored for up to 0.5 s was achieved using time-dependent photodetachment action spectroscopy across the 2Au ← 2B2g and 2B2u ← 2B2g transitions. The rate at which hot-band contributions fade from the action spectrum is quantified by non-negative matrix factorisation. This is found to be commensurate with the average vibrational energy extracted from the simulations, with 1/e lifetimes of 0.16(3) s and 0.1602(7) s, respectively. Implications for astrochemistry are discussed.

Item Type: Article
Additional Information: Acknowledgements: This work was supported by the Swedish Research Council (Grant numbers 2016-03675, 2016-04181, 2018-04092 and 2020-03437), the Olle Engkvist Foundation (Grant number 200–575), and the Swedish Foundation for International Collaboration in Research and Higher Education (STINT, grant number PT2017-7328 awarded to JNB and MHS). We acknowledge the DESIREE infrastructure for provisioning of facilities and experimental support, and thank the operators and technical staff for their invaluable assistance, especially Mikael Björkhage who developed the ion source used in this experiment. The DESIREE infrastructure receives funding from the Swedish Research Council under the Grant numbers 2017-00621 and 2021-00155. This article is based upon work from COST Action CA18212 - Molecular Dynamics in the GAS phase (MD-GAS), supported by COST (European Cooperation in Science and Technology).
Uncontrolled Keywords: physics and astronomy(all),physical and theoretical chemistry ,/dk/atira/pure/subjectarea/asjc/3100
Faculty \ School: Faculty of Science > School of Chemistry
UEA Research Groups: Faculty of Science > Research Groups > Centre for Photonics and Quantum Science
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Depositing User: LivePure Connector
Date Deposited: 24 May 2022 14:59
Last Modified: 09 Feb 2023 13:50
DOI: 10.1039/D2CP00490A


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